"On-line" methods provide insights into the time course of language processing. Project 4 proposes a series of on-line experiments to investigate the temporal microstructure of auditory language processing in normally developing children, under normal processing conditions and under abnormal conditions designed to stimulate the processing deficits hypothesized to underlie some forms of developmental language impairment (i.e., perceptual degradation, to stimulate processing with a deficient perceptual mechanism; compressed speech, to simulate deficits in temporal integration). We will document developmental changes in real-time word and sentence processing across the period from 5 years to adolescence, and compare those results with the processing profiles observed in our clinical populations. Experiments will focus on different tasks and sentence processing across the period from 5 years to adolescence, and compare those results with the processing profiles observed in our clinical populations. Experiments will focus on different tasks and modalities, including (1) sentence interpretation, using stimuli that vary in syntactic complexity and in the point in time at which the listener can make an unambiguous interpretation; (2) grammaticality judgment, focusing on developmental changes in accuracy and reaction time to violations of grammatical morphology, an area that is known to be particularly vulnerable in children with developmental language disorders; (3) word comprehension, in and out of a sentence context, looking at the amount of phonetic information that children of different ages need in order to recognize and repeat a target word, and at developmental changes in the facilitative and/or inhibitory contributions of sentential context on accuracy and reaction time; (4) word production, in and out of a sentence context, looking at developmental changes in the relative contribution of semantic and phonetic cues to accuracy, word onset latency and word duration in a picture-naming task. In collaboration with the other projects in the Center, we will compare the temporal processing profiles that emerge in our "on-line" tasks with performance by children in "off-line" measures of language ability (with Dr. Reilly, 'on-line' processing of nonlinguistic stimuli (with Dr. Stiles), and electrophysiological studies of real-time language processing (with Miles). Finally, we will conduct pilot studies of lexical and grammatical processing in children who are acquiring Italian, a richly inflected language that permits a more detailed examination of developmental changes in real-time processing of grammatical morphology, an area of language that is known to be particularly vulnerable in populations of children and adults with language disorders.